IMPROVED DOUBLE-MULTIPLE STREAMTUBE MODEL FOR THE DARRIEUS-TYPE VERTICAL AXIS WIND TURBINE.

Abstract

Double streamtube codes model the curved blade (Darrieus-type) vertical axis wind turbine (VAWT) as a double actuator-disk arrangement (one disk for the upwind half of the rotor and a second disk for the downwind half) and use conservation of momentum principles to determine the forces acting on the turbine blades and the turbine performance. Sandia National Laboratories has developed a double-multiple-streamtube model for the VAWT which incorporates the effects of the incident wind boundary layer, nonuniform velocity between the upwind and downwind sections of the rotor, dynamic stall effects and local blade Reynolds number variations. This paper presents the theory underlying this VAWT model and describes the code capabilities. Code results are compared with experimental data from two VAWTs and with the results from another double-multiple-streamtube and a vortex-filament code.